For more than 20 years the Whitney has been unveiling sunny expansion plans for its Marcel Breuer home on Madison Avenue, only to have them crash against the reality of neighborhood politics. With its decision to build a second museum in the meatpacking district, the Whitney seems to have found its bearings.

Mr. Piano’s project for a site on Gansevoort Street, west of Washington Street, is a striking departure from the ethereal glass creations that have made him a favorite of the art-world cognoscenti. Its bold chiseled form won’t appeal to those who prefer architecture to be unobtrusive.

Rising among the derelict warehouses and hip boutiques of the rapidly changing neighborhood, the museum’s monumental exterior forms are conceived as a barrier against the area’s increasingly amusement-park atmosphere. It makes a powerful statement about the encroaching effects of the global consumer society. Inside, Mr. Piano has created a contemplative sanctuary where art reasserts its primary place in the cultural hierarchy.

The feat is especially impressive given the obstacles Mr. Piano and the Whitney have overcome. After they spent years refining a proposed addition to the Breuer building, the museum abandoned that plan in 2006 (the third time that the museum had pulled out after commissioning a noted architect to design a major expansion). Then the idea of a satellite downtown raised concerns that the Whitney would abandon its Breuer building or that it could not afford to run two museums.

In a recent interview Adam Weinberg, the Whitney’s director, said the curators had yet to define the relationship between the two buildings. (One possibility is that the Breuer building will be used for exhibitions that focus on one aspect of the collection or a single artist, with the core of the collection relocated downtown.)

Mr. Piano’s design is certainly distinct from Breuer’s, presenting a strange, even forbidding aura. The building’s faceted surface seems hewed from a massive block of stone. Its main facade is slightly angled to make room for a small public plaza. The roof steps down in a series of big terraces on one side; on the other, it forms an impenetrable block facing the West Side Highway.

But as you study the form more intently, more layered meanings emerge. The stepped roof, for example, both supports a series of outdoor sculpture gardens and allows sunlight to spill down onto the High Line, the elevated rail bed that is being converted into a public garden. The angle of the facade allows people walking along the High Line to catch glimpses of the Hudson River down Gansevoort Street.

The feeling of a structure being carved apart to facilitate the flow of light and movement is magnified at ground level. Part of the structure rests on a glass base that houses a bookstore and cafe, so that you feel the full weight of the building bearing down. The underbelly of the building tilts up at one end, providing shade for the plaza and adding a sense of compression as you approach the entry.

This experience abruptly changes as you cross the threshold, for a window at the back of the lobby opens onto a view of the water and the height of the lobby space suddenly lets you breathe again. From there elevators whisk you up to the auditorium, library and galleries.

The new museum will have 50,000 square feet of gallery space, compared with 32,000 uptown. The third-floor gallery, at 17,500 square feet, will be the largest column-free space for viewing art in Manhattan, Mr. Weinberg said.

Mr. Piano plans to use a weblike structure of delicate steel, glass and fabric scrims for the roof on the top-floor gallery: the kind of intricate lighting system he has created before, in projects like the Nasher Sculpture Center in Dallas. Because the galleries are on multiple levels, visitors can experience the drama of climbing from darkness into light as they proceed through the floors.

The contrast between the muscularity of the exterior and the refinement of the interior brings to mind other recent designs, including Rem Koolhaas’s Casa da Musica in Porto, Portugal, and Rafael Moneo’s Cathedral of Our Lady of the Angels in Los Angeles. Each of these projects offer an enclave conceived as a refuge from the world outside.

But in this case Mr. Piano is also offering a gentle critique of Breuer’s fortresslike vision for the Whitney. Like Breuer’s 1966 design, Mr. Piano’s building is a temple to culture; but here the relationship between inside and out — high art and the marketplace — is more fluid.

The design is preliminary, and needs more work. The weblike roof system, for example, is nothing more than a concept at this point. Mr. Piano is toying with the notion of bringing daylight into the lower-floor galleries — as the Sanaa design did for the recently opened New Museum on the Bowery — which is possible here because of the terraced roof.

Just as important to the outcome of the design, however, is Mr. Piano’s approach to New York’s evolving cultural scene. He and Mr. Weinberg refer to the downtown site as a return to the museum’s roots, because Gertrude Vanderbilt Whitney’s original museum opened on West Eighth Street. But unlike 1930s Greenwich Village, the meatpacking district is more shopping mall than vibrant art scene. So one of Mr. Piano’s most delicate tasks will be to balance a spirit of openness with an instinct for self-preservation.

He has wisely decided not to link the building directly to the High Line, forcing visitors to climb down to street level before entering the museum across the plaza. Yet other key issues are less resolved. The building’s chiseled aesthetic could be pushed a bit further, becoming more animated. The relationship between the lobby and the upper floors is still clunky.

And there is the issue of material. At a meeting last month Mr. Piano, who often uses the metaphor of a ship in dry dock when talking about the satellite museum, said he was leaning toward a steel frame structure covered in welded steel plates, an idea that may be a holdover from his abandoned design for the uptown expansion. But the massive form of the downtown design suggests a building drawn from a single block rather than one built of individual structural pieces.

That image would probably be strengthened by cladding the building in a stone compound. A concrete exterior could also form a psychological bridge between the new museum and the Breuer building, making a trip downtown feel more like a homecoming.

Mr. Piano certainly has the skill to resolve these issues. Meanwhile he has laid the groundwork for a serious work of architecture. The bold form expresses a level of experimental courage that he hasn’t shown in years. It represents his willingness to move forward without betraying his faith in historical continuity. This is a building that could revive the Whitney, and inject welcome creative energy into the city’s cultural life.